Articles prepared from degradable materials are becoming increasingly important in view of findings that certain materials, such as plastics, remain intact over long periods of time. In the environment, articles made from materials that do not degrade sufficiently are having conspicuously harmful and deleterious effects. For the ocean environment in particular, it has been recently noted that even small, virtually non-degradable articles such as plastic artificial fishing worms used to bait a recreational fisherman's hooks have been found intact in the oceans and digestive tracts of marine mammals. Given artificial bait's popularity among recreational fishermen, and as discussed below, given the commercial fishermen's increasing need for artificial baits, a degradable version of the article would be strongly desirable.
Artificial fishing bait has become especially popular with all types of fishermen. For instance, recreational fishermen find this type of bait attractive because it is easy to store in a tackle box and it avoids the sometimes distasteful chore of handling and using natural bait such as worms or squid. However, recreational fishing represents just a small portion of fishing activity. Commercial fishing activity represents the larger portion of the fishing market and could benefit from an artificial bait in various ways.
For instance, artificial bait could be stored for long fishing expeditions without worrying about the refrigeration normally required for natural bait. The bait, which can be delivered in dry form, weighs much less than natural bait. It is anticipated that a ton of natural bait can be replaced by a couple hundred pounds of the degradable bait. Similar savings on volume are also possible. In addition, if made in sheet form, the bait could be delivered to and stored in commercial fishing vessels in rolls, for ease of handling. Even further, with the advent of automatic baiting for commercial longline fishing vessels, such rolls can be more safely incorporated into a baiting procedure so that the bait is cut and attached to hooks as the bait sheet unwinds from the roll.
Using this type of bait would be likely to reduce accidents which sometimes occur when using automatic baiting of natural bait. Specifically, natural bait does not always have a uniform size nor is it always in a shape that is easily hooked. As a result, using natural bait requires that someone continuously feed the bait operation and manually place the bait in the slicer of the automatic baiter. This activity sometimes leads to the accidental cutting or hooking of hands or fingers. On the other hand, sheets of artificial bait can be cut to a uniform size and fed to the hooks of the baiting equipment in a manner such that little manual handling is required.
Moreover, artificial bait can be more durable. Natural bait begins to lose its integrity after a period of time in the water and bait can be lost by falling off the hook, or by sea gulls and small fish tearing the bait off the hook. If designed properly, artificial bait can remain on the line for logger periods of time and made strong enough so that it is not easily removed by tearing. In the end, such durability will likely result in larger catch yields.
However, as has been shown, the drawback to the artificial baits on the market today is that they do not possess sufficient degradability. For instance, various bait constructions presently use poly(vinyl chloride), lead jigs and other plastic materials. All of these are believed to be essentially non-degradable materials. See U.S. Pat. Nos. 4,731,247 issued to Wolford et al., Mar. 15, 1988 (cellulose ether and plasticizers); 4,666,717 issued to Smith et al., May 19, 1987 (polyamines and copolymers of ethylene and ethylenically unsaturated monomers); 3,684,519 issued to Combs, Aug. 15, 1972 (polyacrylamide and monomers); and PCT Application 87/07476 (polyurethane foams). As an example, artificial baits such as the well-known plastic worms are prepared from poly(vinyl chloride) and have been known to remain intact for many years. As recently reported, such plastic worms are being found in the digestive tracts of sea otters. Thus, the harmful effects of using such articles are just beginning to manifest themselves, and if commercial fishermen are forced to look for alternatives to natural bait, a degradable artificial alternative would certainly be desired. Likewise, other industries and markets would benefit from degradable articles.
Various degradable materials which might be adapted for use as a degradable bait are known. For example, U.S. Pat. No. 4,132,839, issued to Moran et al. Jan. 2, 1979, discloses prepolymers which, when foamed, provide biodegradable hydrophilic polyurethane foams. The question of how or whether such foams might be incorporated in a degradable bait which is palatable to fish and with sustained release capabilities is not addressed. A bait which can release an attractant in a controlled manner has been proposed in U.S. Pat. No. 4,245,520, issued to Carr Jan. 20, 1981. Its formulation produced a gel which must be refrigerated or frozen. U.S. Pat. No. 4,463,018, issued to Carr Jul. 31, 1984, used gelatin, agar, locust bean gum, partially hydrolyzed cellulose, sorbic acid, and humectants such as glycerol, thus producing a material having improved heat stability and shelf life at the expense of palatability to fish.
Another reference, U.S. Pat. No. 3,410,689, issued to Nathan Nov. 12, 1968, discloses a polyurethane foam mixed with an attractant as a bait which "disjoins," or breaks into relatively large pieces upon immersion in water. This bait relies on the break-up of the article to distribute the attractant.